ELECTROCHEMICALLY SWITCHED ANION TRANSLOCATION IN A MULTICOMPONENT COORDINATION COMPOUND

Complex [3a]2+ has been synthesized, which contains one NiII cyclam-like and one bipyridine fragment (cyclam = 1,4,8,11-tetraazacyclotetradecane). Spectrophotometric and potentiometric titration experiments in aqueous solution demonstrated that in the examined pH range (2−10), the NiII cyclam-like subunit remains square planar, i.e., it does not interact with the bipyridine unit, which is instead allowed to bind external metal centers. In particular, in the presence of 0.5 equiv of CuII, the trinuclear multicomponent coordination compound [CuII(3a)2(H2O)]6+ is the only species existing in solution over a wide pH range. The water molecule bound to the CuII center can be substituted by inorganic anions, forming [CuII(3a)2(anion)]5+ species, and the binding constants of a series of mononegative anions have been determined, demonstrating the effectiveness of [CuII(3a)2(H2O)]6+ as an anion receptor. Voltammetric experiments have shown that the two NiII centers in [CuII(3a)2(H2O)]6+ can be reversibly oxidized t...